More than 11 million Americans report chronic pain as a significant disability. The financial burden of chronic pain in the United States alone is estimated at higher than $100 billion a year, including lost productivity and medical expenses. Viewed globally, there is a large underserved population for pain management medications and/or therapies.
Chronic pain is typically classified as pain lasting more than 6 months and generally divided into three main types: nociceptive, psychogenic or neuropathic (e.g., due to nerve injury) although the distinction between these types can be blurred. Especially true for chronic neuropathic pain, current treatment options including opioids and nonsteroidal anti-inflammatory drugs (e.g. COX inhibitors) are often ineffective, contraindicated or associated with significant gastrointestinal and cardiac side effects, sedation, respiratory depression, addiction and drug abuse. It is widely believed that pharmacotherapy, surgical ablation, and externally applied non-drug therapies (e.g. transcutaneous electrical nerve stimulation and acupuncture) have all reached a ceiling well below the desired level of patients and clinicians. Novel ideas are thus needed in pain research.